Join Date: Jan 2010
Location: Fountain Valley California
The wiring can be checked some by doing this>>>> With power off, pin A at the disconnect goes back to the ECM and is grounded internally. It says you want to see less than 5 ohms from pin A to any convenient ground source close by.
If I understand this correctly, with the ignition in the *on* position, you should read about 450 mv on pin B when going to ground, or back thru pin A.
Pin C goes back to the ECM and is triggered to become a ground, whenever the ECM says so. It becomes the return path to ground, for the heater circuit within the sensor (pretty sure the engine has to be running to set that ground).
Pin D at ignition turn on, is supplied with 12 vdc to power the heater. If you get some good numbers from this, you might be able to eliminate the ECM
Not knowing what goes on with sensor placement with LTs installed, is it possible that extension harnesses had to be installed (which would add even another connector in the loop) ?
The dealer could hook up the scan device, an perform a lot of checks to verify the operation of this circuit, but if they are locked into the upstream sensor as the problem (an you now know better), it might become a no joy situation, and money also being pulled from your wallet.
The T/S you have performed seems to have eliminated the sensors as being the bad guys here.